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  <meta name="description" content="前言昨天更新了一下lfunctimer，主要把hook更改为c api的形式，并且初步加了util和config的扩展 想要试用的同学的话可以点击上面clone下来，或者安装luarocks后执行下面命令安装~ luarocks install --server=http://luarocks.org/manifests/utmhikari lfunctimer 言归正传，利用lua原生的c ap">
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          <h2 class="post-title" itemprop="name headline">【Lua杂谈】debug.getinfo源码分析——使用C API重写lfunctimer

              
            
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        <h2 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h2><p>昨天更新了一下<span class="exturl" data-url="aHR0cHM6Ly9naXRodWIuY29tL3V0bWhpa2FyaS9sZnVuY3RpbWVy" title="https://github.com/utmhikari/lfunctimer">lfunctimer<i class="fa fa-external-link"></i></span>，主要把hook更改为c api的形式，并且初步加了util和config的扩展</p>
<p>想要试用的同学的话可以点击上面clone下来，或者安装<span class="exturl" data-url="aHR0cHM6Ly9sdWFyb2Nrcy5vcmcv" title="https://luarocks.org/">luarocks<i class="fa fa-external-link"></i></span>后执行下面命令安装~</p>
<p><code>luarocks install --server=http://luarocks.org/manifests/utmhikari lfunctimer</code></p>
<p>言归正传，利用lua原生的c api做debug相关操作会比lua自带的<code>debug.getinfo</code>来的快许多，我们可以来一探究竟</p>
<h2 id="debug-getinfo源码分析"><a href="#debug-getinfo源码分析" class="headerlink" title="debug.getinfo源码分析"></a>debug.getinfo源码分析</h2><p>我们可以从官方下载源码搜索<code>debug.getinfo</code>的实现，此处以版本5.3.5为例。</p>
<p><code>debug.getinfo</code>对应的源码是<code>ldblib.c</code>的<code>db_getinfo</code>函数，我们可以简单在<code>ldblib.c</code>的末尾中查到~</p>
<a id="more"></a>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">static</span> <span class="keyword">const</span> luaL_Reg dblib[] = &#123;</span><br><span class="line">  <span class="comment">// 略过前面</span></span><br><span class="line">  &#123;<span class="string">"getinfo"</span>, db_getinfo&#125;,</span><br><span class="line">  <span class="comment">// 略过后面</span></span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="function">LUAMOD_API <span class="keyword">int</span> <span class="title">luaopen_debug</span> <span class="params">(lua_State *L)</span> </span>&#123;</span><br><span class="line">  luaL_newlib(L, dblib);</span><br><span class="line">  <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>lua提供一个注册表（Registry）机制去把我们的函数名跟函数对应起来，然后最后要让lua识别这个模块的话，就定义一个函数，名称为<code>luaopen_模块名</code>，然后通过<code>luaL_newlib</code>方法读取前面的<code>luaL_Reg</code>注册表数据变成一个函数名——函数的table就ok了。</p>
<p>像<code>debug</code>之类的lua内置库，则在起lua的时候就调用<code>linit.c</code>里的<code>luaL_openlibs</code>方法就载入；而如果是第三方库，你在require的时候，则会通过<code>loadlib.c</code>中的方法去寻找模块有无载入过，如果载入过则用载入过的模块(<code>package.loaded</code>)，如果没载入过就载入，并且加到载入过模块中。这部分不再细究啦，有兴趣的同学可以自行发掘，我有空的话也会自己再踩踩坑~</p>
<p>我们再回头看<code>ldblib.c</code>的<code>db_getinfo</code>函数，也就是<code>debug.getinfo</code>对应的实现，代码如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// debug.getinfo([thread,] f [,what]): 获取当前运行函数的信息</span></span><br><span class="line"><span class="comment">// thread (optional): 要获取函数所在的lua state（默认当前lua state）</span></span><br><span class="line"><span class="comment">// f: 调用栈层次（0是当前函数，1是当前函数caller，往上类推）</span></span><br><span class="line"><span class="comment">// what (optional)：获取的信息有哪些（默认全部）</span></span><br><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">int</span> <span class="title">db_getinfo</span> <span class="params">(lua_State *L)</span> </span>&#123;</span><br><span class="line">  lua_Debug ar;</span><br><span class="line">  <span class="keyword">int</span> arg;</span><br><span class="line">  <span class="comment">// 参数检验部分</span></span><br><span class="line">  lua_State *L1 = getthread(L, &amp;arg);  <span class="comment">// 读取thread参数</span></span><br><span class="line">  <span class="keyword">const</span> <span class="keyword">char</span> *options = luaL_optstring(L, arg+<span class="number">2</span>, <span class="string">"flnStu"</span>);</span><br><span class="line">  checkstack(L, L1, <span class="number">3</span>);</span><br><span class="line">  <span class="comment">// 获取func本身/CallInfo</span></span><br><span class="line">  <span class="keyword">if</span> (lua_isfunction(L, arg + <span class="number">1</span>)) &#123;  <span class="comment">/* info about a function? */</span></span><br><span class="line">    options = lua_pushfstring(L, <span class="string">"&gt;%s"</span>, options);  <span class="comment">/* add '&gt;' to 'options' */</span></span><br><span class="line">    lua_pushvalue(L, arg + <span class="number">1</span>);  <span class="comment">/* move function to 'L1' stack */</span></span><br><span class="line">    lua_xmove(L, L1, <span class="number">1</span>);</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">else</span> &#123;  <span class="comment">/* stack level */</span></span><br><span class="line">    <span class="keyword">if</span> (!lua_getstack(L1, (<span class="keyword">int</span>)luaL_checkinteger(L, arg + <span class="number">1</span>), &amp;ar)) &#123;</span><br><span class="line">      lua_pushnil(L);  <span class="comment">/* level out of range */</span></span><br><span class="line">      <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">    &#125;</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="comment">// 获取附加信息flnStu之类的</span></span><br><span class="line">  <span class="keyword">if</span> (!lua_getinfo(L1, options, &amp;ar))</span><br><span class="line">    <span class="keyword">return</span> luaL_argerror(L, arg+<span class="number">2</span>, <span class="string">"invalid option"</span>);</span><br><span class="line">  <span class="comment">// push table，作为最后结果</span></span><br><span class="line">  lua_newtable(L);  <span class="comment">/* table to collect results */</span></span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'S'</span>)) &#123;</span><br><span class="line">    settabss(L, <span class="string">"source"</span>, ar.source);</span><br><span class="line">    settabss(L, <span class="string">"short_src"</span>, ar.short_src);</span><br><span class="line">    settabsi(L, <span class="string">"linedefined"</span>, ar.linedefined);</span><br><span class="line">    settabsi(L, <span class="string">"lastlinedefined"</span>, ar.lastlinedefined);</span><br><span class="line">    settabss(L, <span class="string">"what"</span>, ar.what);</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'l'</span>))</span><br><span class="line">    settabsi(L, <span class="string">"currentline"</span>, ar.currentline);</span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'u'</span>)) &#123;</span><br><span class="line">    settabsi(L, <span class="string">"nups"</span>, ar.nups);</span><br><span class="line">    settabsi(L, <span class="string">"nparams"</span>, ar.nparams);</span><br><span class="line">    settabsb(L, <span class="string">"isvararg"</span>, ar.isvararg);</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'n'</span>)) &#123;</span><br><span class="line">    settabss(L, <span class="string">"name"</span>, ar.name);</span><br><span class="line">    settabss(L, <span class="string">"namewhat"</span>, ar.namewhat);</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'t'</span>))</span><br><span class="line">    settabsb(L, <span class="string">"istailcall"</span>, ar.istailcall);</span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'L'</span>))</span><br><span class="line">    treatstackoption(L, L1, <span class="string">"activelines"</span>);</span><br><span class="line">  <span class="keyword">if</span> (<span class="built_in">strchr</span>(options, <span class="string">'f'</span>))</span><br><span class="line">    treatstackoption(L, L1, <span class="string">"func"</span>);</span><br><span class="line">  <span class="keyword">return</span> <span class="number">1</span>;  <span class="comment">/* return table */</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>可以看到如果在每次调用<code>debug.getinfo</code>会经历<code>参数检验——获取func或CallInfo信息——获取附加信息（what）</code>的过程，每次都会创建一个<code>lua_Debug</code>结构体，在lua中返回的是一个table，相对繁琐一些。为了提高效率，我们可以直接用<code>db_getinfo</code>中的<code>lua_getstack</code>跟<code>lua_getinfo</code>方法去在我们的c hook中获取函数信息。</p>
<h2 id="用C-API重写lfunctimer的hook"><a href="#用C-API重写lfunctimer的hook" class="headerlink" title="用C API重写lfunctimer的hook"></a>用C API重写lfunctimer的hook</h2><p>在新版lfunctimer中，第一版C Hook实现如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">ifndef</span> LFUNCTIMER_UPVAL_IDX</span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">define</span> LFUNCTIMER_UPVAL_IDX 1</span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">endif</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="meta-keyword">ifndef</span> LFUNCTIMER_FUNCMAP_UPVAL_IDX</span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">define</span> LFUNCTIMER_FUNCMAP_UPVAL_IDX 2</span></span><br><span class="line"><span class="meta">#<span class="meta-keyword">endif</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">// push function name to top of stack</span></span><br><span class="line"><span class="comment">// not the same as builtin "getfuncname" method</span></span><br><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">int</span> <span class="title">lfunctimer_getfuncname</span><span class="params">(lua_State *L)</span> </span>&#123;</span><br><span class="line">    lua_Debug ar;</span><br><span class="line">    <span class="keyword">if</span> (!lua_getstack(L,  LFUNCTIMER_STKLVL, &amp;ar)) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// check if function name already exists</span></span><br><span class="line">    lua_getinfo(L, <span class="string">"f"</span>, &amp;ar);</span><br><span class="line">    lua_pushvalue(L, <span class="number">-1</span>);</span><br><span class="line">    lua_gettable(L, lua_upvalueindex(LFUNCTIMER_FUNCMAP_UPVAL_IDX));</span><br><span class="line">    <span class="keyword">if</span> (lua_toboolean(L, <span class="number">-1</span>)) &#123;</span><br><span class="line">        lua_remove(L, <span class="number">1</span>);  <span class="comment">// remove funcinfo</span></span><br><span class="line">        <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    lua_pop(L, <span class="number">1</span>);</span><br><span class="line">    <span class="comment">// check if it's a builtin function</span></span><br><span class="line">    lua_getinfo(L, <span class="string">"Sn"</span>, &amp;ar);</span><br><span class="line">    <span class="keyword">const</span> <span class="keyword">char</span> *what = ar.what;</span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">strcmp</span>(what, <span class="string">"C"</span>) == <span class="number">0</span>) &#123;</span><br><span class="line">        lua_pushfstring(L, <span class="string">"&lt;Builtin&gt; %s"</span>, ar.name);</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> (ar.namewhat[<span class="number">0</span>] == <span class="string">'\0'</span>) &#123;</span><br><span class="line">        lua_pushfstring(L, <span class="string">"&lt;%s:%d&gt; ::UNKNOWN::"</span>, ar.short_src, ar.linedefined);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        lua_pushfstring(L, <span class="string">"&lt;%s:%d&gt; %s"</span>, ar.short_src, ar.linedefined, ar.name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// save function name to function map</span></span><br><span class="line">    lua_pushvalue(L, <span class="number">1</span>);</span><br><span class="line">    lua_pushstring(L, lua_tostring(L, <span class="number">-2</span>));</span><br><span class="line">    lua_settable(L, lua_upvalueindex(LFUNCTIMER_FUNCMAP_UPVAL_IDX));</span><br><span class="line">    <span class="comment">// remove funcinfo</span></span><br><span class="line">    lua_remove(L, <span class="number">1</span>);</span><br><span class="line">    <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>在某些情况下（比如loadstring）时，我们希望能够不侵入lua原生api去获取函数名称信息。因此可以这样操作——在hook函数中去上一个栈层次（level=1）的caller，我们就可以<code>getstack</code>后把函数信息暂存在一个<code>lua_Debug</code>结构体中，并在后续依据需求<code>getinfo</code>相应的内容。</p>
<p>获取函数名称的总体逻辑和上一版的lfunctimer（lua hook）基本类似，如果能获取到好书名称，就把函数名称push到<code>lua_State</code>的栈上。在后边的逻辑中，call跟return事件的handler都被分离了出来，这样就显得更加模块化了。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// debug hook of lfunctimer</span></span><br><span class="line"><span class="function"><span class="keyword">static</span> <span class="keyword">int</span> <span class="title">lfunctimer_debug_hook</span><span class="params">(lua_State *L)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">const</span> <span class="keyword">char</span> *evt = lua_tostring(L, <span class="number">1</span>);</span><br><span class="line">    lua_settop(L, <span class="number">0</span>);</span><br><span class="line">    <span class="comment">// get function name</span></span><br><span class="line">    <span class="keyword">if</span> (lfunctimer_getfuncname(L) == <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// print log</span></span><br><span class="line">    lua_getfield(L, lua_upvalueindex(LFUNCTIMER_CFG_UPVAL_IDX), <span class="string">"verbose"</span>);</span><br><span class="line">    <span class="keyword">if</span> (lua_toboolean(L, <span class="number">-1</span>)) &#123;</span><br><span class="line">        lua_getfield(L, lua_upvalueindex(LFUNCTIMER_UPVAL_IDX), <span class="string">"log"</span>);</span><br><span class="line">        lua_pushfstring(L, <span class="string">"%s: %s"</span>, lua_tostring(L, <span class="number">1</span>), evt);</span><br><span class="line">        lua_call(L, <span class="number">1</span>, <span class="number">0</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    lua_pop(L, <span class="number">1</span>);</span><br><span class="line">    <span class="comment">// dispatch events</span></span><br><span class="line">    <span class="keyword">if</span> (evt[<span class="number">0</span>] == <span class="string">'c'</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> handle_call(L);</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> (evt[<span class="number">0</span>] == <span class="string">'r'</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> handle_return(L);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>过后真的要多抽空研读下各种源码，打好基础= =mlgb的，最近为了领导毕业论文的事情，都憔悴了。</p>

      
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